This invention relates to an angular velocity sensor, and more particularly to an angular velocity sensor suitable for mass-production utilizing micromachining technology and semiconductor technology.
In the automobile industry or machinery industry, etc., there has been increased demand for sensors capable of precisely detecting acceleration or angular velocity of a moving object. In regard to an acceleration, sensors of various types have been conventionally proposed, and small-sized sensors capable of two-dimensionally or three-dimensionally detecting an applied acceleration have been put into practical use. For example, in the International Publication No. W088/08522 based on the Patent Cooperation Treaty (U.S. Pat. Nos. 4,967,605, 5,182,515), an acceleration sensor utilizing changes of resistance values of piezo resistance elements formed on a semiconductor substrate is disclosed. Moreover, in the International Publication No. W092/17759 based on the Patent Cooperation Treaty (U.S. Pat. No. 5,492,020), there is disclosed an acceleration sensor in which electrostatic capacitance elements or piezoelectric elements are used to detect an applied acceleration in every respective coordinate axis direction. In the International Publication No. W093/02342 based on the Patent Cooperation Treaty (U.S. Pat. No. 5,365,799), there is disclosed a multi-axial acceleration sensor using piezoelectric elements of different type.
On the other hand, there are a relatively few publications in connection with the angular velocity sensor. Particularly, publications in regard to angular velocity sensors capable of simultaneously detecting angular velocity about multi-axes can be hardly seen. Ordinarily, angular velocity sensors are utilized for the purpose of detecting an angular velocity of a power shaft, etc. of vehicle, and only have a function to detect an angular velocity about a specific one axis. In such a case that a rotational speed of the power shaft as described above is measured, it is sufficient to use a one-dimensional angular velocity sensor. However, as a sensor for detecting angular velocity with respect to an object which carries out free movement within a three-dimensional space, multi-axial velocity sensors capable of simultaneously detecting angular velocity components about two-axes or three-axes are expected.
In order to meet with such demand, the inventor of this application has proposed novel multi-axial angular velocity sensors in the International Publication No. W094/23272 based on the Patent Cooperation Treaty (U.S. patent application Ser. No. 08/366,026) and the Japanese Patent Application No. 7-56690/1995 specification (U.S. patent application Ser. No. 08/601,794). Such novel angular velocity sensors utilize the principle that when an angular velocity is applied about the second coordinate axis to the object moving in the first coordinate axial direction in the XYZ three-dimensional rectangular coordinate system, Coriolis force is produced in the third coordinate axial direction, and the sensors detect the Coriolis force applied to the object so as to indirectly detect an angular velocity. For detecting Coriolis force, the technologies which have been fostered in the conventional acceleration sensors are applied. That is, a piezo resistance element, a capacitance element and a piezoelectric element, etc. are utilized.
An object of this invention is to provide a concrete and more practical mechanism of the angular velocity sensor based on the above-described principle, particularly to provide a novel technique for manufacturing a multi-axial angular velocity sensor utilizing micromachining technology and semiconductor technology, According to this invention, mass-production of small and high accuracy multi-axial angular velocity sensors is realized.
(1) The first feature of the present invention resides in an angular velocity sensor comprising:
a substrate having an upper surface along an XY plane in an XYZ three-dimensional coordinate system;
a weight body for carrying out rotational movement in a non-contact state with respect to the upper surface with a Z-axis perpendicular to the upper surface being an axis of rotation; energy supply means for delivering energy to the weight body so that the weight body carries out the rotational movement while maintaining a fixed distance with respect to the upper surface of the substrate when no external force is applied; and
xe2x80x9cdistance above X-axis measurement meansxe2x80x9d for measuring a distance between the upper surface and the weight body at a time when the weight body passes above the X-axis;
thus to detect an angular velocity about the X-axis on the basis of a distance measured by the distance above X-axis measurement means.
(2) The second feature of the present invention resides in an angular velocity sensor as in the first feature: and
wherein there are provided a first weight body and a second weight body which carry out the rotational movement in a non-contact state with respect to the upper surface of the substrate with the Z-axis being as an axis of rotation;
wherein the first weight body and the second weight body can be rotated in a state where their phases are shifted relative to each other by 180 degrees so that when the first weight body is positioned above the positive X-axis, the second weight body is positioned above the negative X-axis; and
the xe2x80x9cdistance above positive X-axis measurement meansxe2x80x9d serves for measuring the distance between the upper surface of the substrate and either of the weight bodies at a time when the weight body passes above the positive X-axis;
the xe2x80x9cdistance above negative X-axis measurement meansxe2x80x9d serves for measuring a distance between the upper surface of the substrate and either of the weight bodies at a time when the weight body passes above the negative X-axis; and
difference calculation means for obtaining a difference between the distance measured by the xe2x80x9cdistance above positive X-axis measurement meansxe2x80x9d and the distance measured by the xe2x80x9cdistance above negative X-axis measurement meansxe2x80x9d,
thus to detect an angular velocity about the X-axis applied to the substrate on the basis of a difference obtained by the difference calculation means.
(3) The third feature of the present invention resides in an angular velocity sensor according to the first feature:
wherein there is further provided xe2x80x9cdistance above Y-axis measurement meansxe2x80x9d for measuring a distance between the upper surface of the substrate and the weight body at a time point when the weight body passes above the Y-axis;
thus to detect an angular velocity about the X-axis applied to the substrate on the basis of the distance measured by the xe2x80x9cdistance above X-axis measurement meansxe2x80x9d, and to detect an angular velocity about the Y-axis applied to the substrate on the basis of the distance measured by the xe2x80x9cdistance above Y-axis measurement meansxe2x80x9d.
(4) The fourth feature of the present invention resides in an angular velocity sensor according to the third feature:
wherein there are provided a first weight body and a second weight body which carry out rotational movement in a non-contact state with respect to the upper surface of the substrate with the Z-axis being as an axis of rotation;
wherein the first weight body and the second weight body can be rotated in a state where their phases are shifted relative to each other by 180 degrees so that when the first weight body is positioned above the positive X-axis, the second weight body is positioned above the negative X-axis and when the first weight body is positioned above the positive Y-axis, the second weight body is positioned above the negative Y-axis;
wherein there are provided;
xe2x80x9cdistance above positive X-axis measurement meansxe2x80x9d for measuring a distance between the upper surface of the substrate and either of the weight bodies at a time point when the weight body passes above the positive X-axis;
xe2x80x9cdistance above negative X-axis measurement meansxe2x80x9d for measuring the distance between the upper surface of the substrate and either of the weight bodies at a time when the weight body passes above the negative X-axis;
xe2x80x9cdistance above positive Y-axis measurement meansxe2x80x9d for measuring the distance between the upper surface of the substrate and either of the weight bodies at a time point when the weight body passes above the positive Y-axis;
xe2x80x9cdistance above negative Y-axis measurement meansxe2x80x9d for measuring the distance between the upper surface of the substrate and either of the weight bodies at a time point when the weight body passes above the negative Y-axis;
first difference calculation means for obtaining a difference between the distance measured by the xe2x80x9cdistance above positive X-axis measurement meansxe2x80x9d and the distance measured by the xe2x80x9cdistance above negative X-axis measurement meansxe2x80x9d; and
second difference calculation means for obtaining a difference between the distance measured by the xe2x80x9cdistance above positive Y-axis measurement meansxe2x80x9d and the distance measured by the xe2x80x9cdistance above negative Y-axis measurement meansxe2x80x9d;
thus to detect an angular velocity about the X-axis applied to the substrate on the basis of a difference obtained by the first difference calculation means, and to detect an angular velocity about the Y-axis applied to the substrate on the basis of the difference obtained by the second difference calculation means.
(5) The fifth feature of the present invention resides in an angular velocity sensor according to the fourth feature:
wherein there are further provided, in addition to the first weight body and the second weight body, a third weight body and a fourth weight body which carry out rotational movement in a non-contact state with respect to the upper surface of the substrate with the Z-axis being an axis of rotation; and
wherein the first weight body, the second weight body, the third weight body and the fourth weight body are coupled through an intermediate member so that when the first weight body is positioned above the positive X-axis, the second weight body is positioned above the negative X-axis, the third weight body is positioned above the positive Y-axis and the fourth weight body is positioned above the negative Y-axis.
(6) The sixth feature of the present invention resides in an angular velocity sensor according to the second, fourth or fifth feature:
wherein the shapes and masses of the plural weight bodies are the same.
(7) The seventh feature of the present invention resides in an angular velocity sensor according to the first to the sixth features:
wherein a ring-shape structural body to surround the periphery of the Z-axis is prepared to allow the ring-shaped structural body to undergo rotational movement in a non-contact state with respect to the upper surface of the substrate with the Z-axis being an axis of rotation by delivering energy from the energy supply means to the ring-shaped structural body so that a portion of the ring-shaped structural body is considered to be a single weight body which is subject to distance measurement.
(8) The eighth feature of the present invention resides in an angular velocity sensor according to the first to the seventh features:
wherein the rotational movement of the weight body is a continuous rotational movement always having the same rotational direction.
(9) The ninth feature of the present invention resides in an angular velocity sensor according to the eighth feature:
which comprises a pivotal shaft fixed on the upper surface of the substrate in a manner extending along the Z-axis to support the weight body by the pivotal shaft so that the weight body can be moved in the Z-axis direction and a rotational direction with respect to the Z-axis with a predetermined degree of freedom.
(10) The tenth feature of the present invention resides in an angular velocity sensor according to the first to the seventh features:
wherein the weight body carries out a reversal rotational movement such that a rotation in the clockwise direction and a rotation in the counterclockwise direction are alternately repeated.
(11) The eleventh feature of the present invention resides in an angular velocity sensor according to the tenth feature:
wherein there are provided:.
a first weight body carrying out a reversal rotational movement to traverse the positive X-axis;
a second weight body carrying out a reversal rotational movement to traverse the negative X-axis;
a third weight body carrying out a reversal rotational movement to traverse the positive Y-axis; and
a fourth weight body carrying out axe2x80x2 reversal rotational movement to traverse the negative Y-axis;
wherein a rotational direction of the reversal rotational movement of the first weight body and the second weight body and a rotational direction of the reversal rotational movement of the third weight body and the fourth weight body are set to be always opposite each other.
(12) The twelfth feature of the present invention resides in an angular velocity sensor according to the tenth or eleventh feature:
wherein a supporting body made of material capable of producing torsion about the Z-axis is secured on the upper surface of the substrate to support the weight body.
(13) The thirteenth feature of the present invention resides in an angular velocity sensor according to the first to the twelfth features:
wherein at least a portion of the weight body is constituted by a dielectric substance; and
wherein the energy supply means is constituted by plural electrodes disposed along an orbit of the rotational movement of the weight body and a voltage supply circuit for supplying, to the plural electrodes, a.c. voltages whose phases are different from each other.
(14) The fourteenth feature of the present invention resides in an angular velocity sensor according to the first to the thirteenth features:
wherein means for measuring a distance between the weight body passing above a coordinate axis and the upper surface of the substrate is constituted by a movement electrode formed on a lower surface of the weight body, a fixed electrode formed in the vicinity of the coordinate axis on the upper surface of the substrate, and a detection circuit for detecting an electrostatic capacitance value of a capacitance element constituted by the movement electrode and the fixed electrode.
(15) The fifteenth feature of the present invention resides in an angular velocity sensor according to the fourteenth feature:
wherein there are provided a first fixed electrode and a second fixed electrode which are disposed in a manner adjacent to each other;
wherein there is provided an electrically unitary movement electrode which can be opposed to both the first fixed electrode and the second fixed electrode; and
wherein the detection circuit is constituted by a circuit for electrically detecting an electrostatic capacitance value between the first fixed electrode and the second fixed electrode.
(16) The sixteenth feature of the present invention resides in an angular velocity sensor comprising:
a substrate having an upper surface in an XY plane in an XYZ three-dimensional coordinate system;
a weight body for carrying out rotational movement in a non-contact state with respect to the upper surface and a Z-axis perpendicular to the upper surface as an axis of rotation;
energy supply means for delivering energy to the weight body so that the weight body carries out the rotational movement while maintaining a fixed distance with respect to the Z-axis when no external force is applied; and
distance measurement means for measuring a distance between the weight body and the Z-axis;
thus to detect an angular velocity about the Z-axis applied to the substrate on the basis of the distance measured by the distance measurement means.
(17) The seventeenth feature of the present invention resides in an angular velocity sensor according to the sixteenth feature:
wherein there are provided a first weight body and a second weight body which carry out the rotational movement in a non-contact state with respect to the upper surface of the substrate around the Z-axis;
wherein the first weight body and the second weight body can be rotated in a state where their phases are shifted relative to each other by 180 degrees so that when the first weight body is positioned above the positive X-axis, the second weight body is positioned above the negative X-axis; and
wherein there are provided;
xe2x80x9cpassing above positive X-axis distance measurement meansxe2x80x9d for measuring a distance between the Z-axis and either of the weight bodies at a time point when either of the weight bodies passes above the positive X-axis;
xe2x80x9cpassing above negative X-axis distance measurement meansxe2x80x9d for measuring a distance between the Z-axis and either of the weight bodies at a time point when either of the weight bodies passes above the negative. X-axis; and
calculation means for obtaining a sum of the distance measured by the passing above positive X-axis distance measurement means and the distance measured by the passing above negative X-axis distance measurement means;
thus to detect an angular velocity about the Z-axis applied to the substrate on the basis of the sum obtained by the calculation means.
(18) The eighteenth feature of the present invention resides in an angular velocity sensor according to the seventeenth feature:
wherein the rotational movement of the weight body is a continuous rotational movement always having the same rotational direction.
(19) The nineteenth feature of the present invention resides in an angular velocity sensor according to the eighteenth feature:
wherein the first weight body and the second weight body are coupled by an intermediate member having an expanding or contracting property; and
wherein a pivotal shaft fixed on the upper surface of the substrate and extending along the Z-axis is provided to rotatively support the intermediate member.
(20) The twentieth feature of the present invention resides in an angular velocity sensor according to the seventeenth feature:
wherein the weight body carries out a reversal rotational movement such that a rotation in the clockwise direction and a rotation in the counterclockwise direction are alternately repeated.
(21) The twenty-first feature of the present invention resides in an angular velocity sensor according to the twentieth feature:
wherein a supporting body made of material which can produce torsion about the Z-axis is secured on the upper surface of the substrate to support the weight body by the supporting body through an intermediate member having an expanding or contracting property.
(22) The twenty-second feature of the present invention resides in an angular velocity sensor according to the sixteenth to the twenty-first features:
wherein at least a portion of the weight body is constituted with dielectric substance; and
wherein the energy supply means is constituted by plural electrodes disposed along an orbit of the rotational movement of the weight body and a voltage supply circuit for supplying, to the plural electrodes, a.c. voltages whose phases are different from each other.
(23) The twenty-third feature of the present invention resides in an angular velocity sensor according to the sixteenth to the twenty-second feature:
wherein distance measurement means for measuring a distance between the weight body and the Z-axis is constituted by a movement electrode formed on a lower surface of the weight body, a fixed electrode formed at a position shifted by a predetermined offset distance toward the inside or the outside relative to a position opposite the movement electrode, and a detection circuit for detecting an electrostatic capacitance value of a capacitance element constituted by the movement electrode and the fixed electrode.
(24) The twenty-fourth feature of the present invention resides in an angular velocity sensor according to the twenty-third feature:
wherein there are provided a first fixed electrode and a second fixed electrode which are disposed adjacent to each other;
wherein there is provided an electrically unitary movement electrode which can be opposed to both the first fixed electrode and the second fixed electrode; and
wherein the detection circuit is constituted by a circuit for electrically detecting an electrostatic capacitance value between the first fixed electrode and the second fixed electrode.